The present invention relates to a roll blade assembly for a paper coating machine wherein a loading bag pushes a bar unit outwards.
Such an assembly generally incorporates a frame with an attached support to which a blade member is attached at its other end. The front edge of the blade member is provided with a rotating metering bar. An inflatable loading bag in the assembly has been designed to push the bar unit outwards from the support with increasing inflation pressure so that the rotating bar is pressed against the web that runs over the coating cylinder.
These roll blade or metering bar coating assemblies have gained widening use in paper and cardboard coating machines. The greatest benefits of these coating assemblies are their low sensitivity to contamination in the coating material and long service life as compared to conventional doctor blade coating assemblies. In the latter constructions, the blade must normally be changed 2 to 4 times a day. The greatest disadvantage in doctor blade coating is the difficulty of adjusting the coating material thickness.
In conventional metering bar assemblies, the blade member to which the bar unit with the rotating metering bar is attached at the front edge thereof is stiff compared to a typical doctor blade member. Due to this construction, also the reflow of coating material is easily disturbed.